Optimism over the Japanese and U.S. economies has lifted the Nikkei 225 stock average above the 20,000 line, but lingering uncertainty over U.S. President Donald Trump's economic policies may prevent investors from chasing higher ground.

The benchmark average hit the threshold for the first time in 18 months on Friday as a stream of upbeat economic data from both countries sparked buying by overseas investors, who had stayed away from the market following reports over Trump's alleged links to Russia.

Favorable U.S. manufacturing and private-sector jobs data helped lift the dollar against the yen, while stronger than expected Japanese industrial output and corporate investment data raised confidence in the plodding recovery of the world's third-largest economy.